2.1. Technical Field
This invention relates to a plastic film, in particular to transparent or semitransparent film, particularly for agricultural uses, which cuts infrared rays to prevent elevation of interior temperature.
2.2 Description of The Related Art
A variety of functional films are known. Among them, many studies are made to develop plastic films for agricultural uses such as heat absorbing film and a interior heat controlling film from a view point of energy saving.
For example, JP-B-62-41465 and JP-B-62-41865 disclose a heat absorbing film consisting of a laminate having a thin metal film, JP-A-56-32352 and JP-A-63-134332 disclose a infrared reflective laminate comprising dielectric layer and metal layer, JP-B-54-25060, JP-B-58-56533 and JP-B-62-54143 disclose a film including metal complex, JP-A-3-161644 and JP-A-6-214113 disclose a film containing pigment which absorb near infrared region and JP-A-62-210973 and JP-A-2-110137 disclose a film containing ceramic particles which absorb near infrared radiation.
However, known products require sophisticated lamination technique, have a problem in thermal stability of pigments during melt-mixing stage and in nonuniform dispersion.
Usually, the film is made of polyester, polycarbonate, nylon, polyvinylchloride, polyvinylidene chloride, polyethylene, polypropylene, ethylenevinyl acetate copolymer. These film, however, do not possess high resistance to water vapour which is required in packaging material for fruits and vegetables.
An object of the present invention is to provide a plastic film which can reduce transmission of heat, prevent heat generation and possessing high permeability to water vapour, by melt-mixing special inorganic particles in a resin.